There’s been a sea change in how we think about fish.

Old: Fish is good for you.

New: Fish is good for you if it doesn’t have too much mercury. And if it’s not an overfished species. And if it’s not from a fish farm that’s polluting the environment.

If you’re confused, you’re not alone. But help is here — from O, The Oprah Magazine, of all places.

In the June issue, the editors boil the issue down to seven main points:

1. Carry a wallet-size fish list ranking seafood in terms of health and sustainability. Find them at edf.org (the Environmental Defense Fund), mbayaq.org (the Monterey Bay Aquarium in California) and blueocean.org (the Blue Ocean Institute).

2. Eat low on the food chain. Smaller fish, such as sardines, anchovies, farmed trout, fresh tilapia and arctic char, plus bivalves, such as scallops, clams and oysters, have fewer contaminants than larger carnivores.

3. Diversify your seafood diet.

4. Look for seafood certified by the Marine Stewardship Council. For a list of retailers, check out eng.msc.org.

5. Buy Alaskan salmon, halibut and sablefish; consider replacing half the canned tuna in your diet with canned Alaskan salmon.

6. Try something new. If restaurant patrons are more adventurous, chefs can move beyond the 10 or 12 most popular species.

7. Avoid farmed Atlantic salmon. However, farmed freshwater fish, including catfish, barramundi and trout, and bivalves, including oysters and clams, are among the best available choices.Kona Kampachi, a type of yellowtail farmed off the coast of Hawaii, is a smart alternative to wild tuna.